Like the intensely single-minded drummer Miles Teller plays in “Whiplash,” its writer-director, Damien Chazelle, did not arrive on the world stage unprepared. In fact, exactly one year before his white-knuckle feature won Sundance’s grand jury prize, the helmer had collected the equivalent trophy for his short film — a standalone version of the pic’s most intense scene.

It’s nothing new for an indie helmer to spin a well-received short into a feature. After all, that’s how both Wes Anderson (“Bottle Rocket”) and Paul Thomas Anderson (whose “Cigarettes & Coffee” became “Hard Eight”) got their start. But shorts are back in vogue as a showbiz calling card at a time when securing funding for independent films is more elusive than ever. Chazelle belongs to a recent wave of filmmakers — including SXSW breakout Destin Cretton (“Short Term 12”) and Oscar live-action short winner Shawn Christensen (“Curfew”) — who’ve discovered that the only way to direct the films they want is to make them first on a smaller scale.

Of the three directors, Chazelle was the only one with a clear-cut strategy. He had moved to Los Angeles after graduating from Harvard College in 2007 with big dreams, and managed to get his first feature off the ground: a 2009 black-and-white jazz musical called “Guy and Madeline on a Park Bench,” which played the festival circuit, and earned generally positive reviews when it finally played theatrically on five screens more than a year later. He became a writer for hire, penning spec scripts he had no intention of directing (including 2013’s Hitchcock-style Elijah Wood-starrer “Grand Piano”). But “Whiplash” — which will screen at Toronto and open Oct. 10, via Sony Pictures Classics — was different. It was personal, inspired by Chazelle’s experience as a saxophone player, and the approach he envisioned wasn’t something backers could imagine.

“I sent the script around town, and everyone passed on it,” Chazelle says. “I think the challenge lay in how I was pitching it to people. Yes, it was a film about jazz musicians, but I wanted it to play like a thriller or an action movie. I was a newbie director, and so people were essentially telling me, ‘Show me first.’”

Chazelle got his first real encouragement from Couper Samuelson, an exec VP at genre shingle Blumhouse. Still, it was easy to see that “Whiplash” wouldn’t be the next “Paranormal Activity,” so Samuelson recommended the script to Helen Estabrook, Jason Reitman’s producing partner at Right of Way. Reitman had kicked off his own directing career by taking a short, “Operation,” to Sundance in 1998. If potential financiers didn’t get Chazelle’s musical-thriller take, the Right of Way team suggested that he select a portion of the script, shoot it, and treat the resulting short as a sort of “proof of concept.”

“With the influx of material, I don’t think people really read anymore, so a little piece of footage can go further than a 120-page script,” says Chazelle, who picked the rehearsal scene, in which his main character auditions for the elite music conservatory’s tough-as-nails band leader.

“It was handy, because it was one location, and it was a way to introduce our approach, to show that you can put musicians in a room with a teacher, where there are no guns or ticking bombs, and make that feel like life or death,” he says. “If we could make that work, then we knew the movie as a
whole could work.”

Chazelle hadn’t written the band leader with a particular actor in mind. It was Reitman’s idea to reach out to J.K. Simmons, who’d appeared in all five of his features “It was a big gamble. Nobody was getting paid very much on the short, and there was no guarantee that the feature would ever happen or that the cast would stay the same,” Chazelle says. Since they had no time to rehearse, the actors were on their own to flesh out their characters. “In the three days that we shot the short, I went from, ‘Oh, J.K. would be great in the role,’ to, ‘I won’t let anyone else play this role,’ ” the director adds.

Working so quickly, Chazelle didn’t expect to get into Sundance. After all he’d made the short to attract investors. (Indeed, about six months later, Bold Films agreed to back the project.) “Up until the short, my most common relationship with Sundance was rejection,” Chazelle says. The festival had passed on “Guy and Madeline,” and the odds were against him: “Whiplash” was just one of more than 8,000 shorts submitted to Sundance 2013.

“That number had been steadily increasing over the years, and then all of a sudden, with the addition of digital technology, it exploded,” explains Sundance programming director Trevor Groth, who got his start picking shorts for the festival in 1993, when submissions still numbered in the low hundreds.

“With all the tracking people in the industry do now, there’s so much awareness of what’s happening in the feature world,” Groth notes. “So it’s rare to find a film coming through the submission process where no one has heard of it. But with shorts, most of them are unknown. So finding those diamonds in the rough, where you can just feel the director’s future, is exhilarating.”

Unlike Chazelle, Cretton — whose “Short Term 12” won Sundance’s top short-film prize in 2009 — says he had no intention of turning the work into a feature. Still, at the urging of friends, when the festival invited his short to screen, Cretton began to scramble to write a full-length version so he could capitalize on whatever interest it generated.

Drawing from his experience working in a foster-care facility, Cretton had made “Short Term 12” as his master’s thesis at San Diego State U., seeing it as a chance to work with actors and try out certain techniques. “It was surprising to me the number of people that connected to it, he says, “The response was an inspiration to turn it into a feature.”

“Short Term 12” set Cretton back about $4,000 — “mainly because it was shot on film,” he says — and ultimately earned him more than he would later get for directing the full-length movie, after exposure at fests like Sundance and Claremont-Ferrand led to distribution deals with PBS and iTunes. By all standards, the short couldn’t have been more successful, but it still was not enough (at the time) to convince people to make my feature,” he adds.

At first, even Cretton needed convincing. The process didn’t feel organic, as he wrestled to expand upon the short. “But as soon as I changed enough of it, like switching the main character from a male to a female, it felt like a brand new story.” Suddenly, everything felt fresh and exciting again, and the writing came easily.

The script for the feature earned him a Nicholl Fellowship from the Academy. But Instead of living off the $30,000 grant to write his next screenplay (as the prize was intended), Cretton says he went on a ramen-noodle diet, and used the money to fund his super-cheap first feature, “I Am Not a Hipster,” made with friends, and written for locations he knew he could get for free. Ultimately, making “Hipster” convinced financiers they could trust him to direct the “Short Term 12” feature.

Christensen initially dropped about $35,000 on “Curfew,” although buying music rights pushed the cost up to $60,000. He never expected to get that money back, though the Oscar attention led to a distribution deal with ShortsHD, landing it a coveted theatrical run. (“The budget actually escalated because of the nomination,” he says.)

If Christensen had a strategy going in to “Curfew,” it certainly didn’t involve awards attention, much less paving the way for a directing career. (The feature version, “Before I Disappear,” debuted at SXSW and plays in Venice this week.) “It was supposed to be my last hurrah,” he says.

Based in New York, Christensen had sold four scripts, which he’d seen rewritten and eventually shelved. “My confidence as a writer was at an all-time low. I felt like I needed to direct a script I had written to see if I should give up the whole thing altogether,” he says. That explains the tone and subject of “Curfew,” which opens with a guy slitting his wrists in the bathtub.

As “Curfew” began to build a fanbase on the festival circuit — an unusual achievement for a short — Christensen started fleshing it out, wondering if there was a way to expand the characters in another project. He had a script “about 75% done” when Lucan Toh of Wigwam Films offered to finance a feature version. With money for indie films tight these days, he wasn’t about to pass up Toh’s offer.

The examples of Chazelle, Cretton and Christensen reveal just how tough it is for any relatively unproven writer-director to convince someone else to trust their vision. Back in the ’90s, a writer with a hot script could set his own conditions, the way unproven “Boondock Saints” scribe Troy Duffy did when convincing Harvey Weinstein not only to let him direct, but to sweeten the deal by buying his bar. Likewise, “Boiler Room” writer Ben Younger turned down lucrative offers until New Line agreed to let him helm.

Today, writer-directors don’t have that kind of power.

Referring to Chazelle’s situation with “Whiplash,” Groth pinpoints a term gun-shy investors use to nix anything slightly outside the box: “Everyone was passing on it, saying it’s too ‘execution dependent’” — meaning that they can’t see it on the page and don’t trust the director to pull off something beyond their capacity to visualize. “It’s a funny concept, but what a short film can do is demonstrate what that execution might be,” Groth says.

Still, he cautions against the calling-card method, where successes are still relatively rare, suggesting that the best shorts tend to be organic -such as “Curfew” and “Short Term 12.” “We see hundreds of shorts submitted to us where they think, ‘My intention is to make this, and then I’ll be able to set up my feature,’ ” says the Sundance programming chief. “But you still need to have an understanding of the short film, which I believe is an art form in its own right, the way writing short stories is different from novels.”

Though Sundance has debuted many indies that originated as shorts over the years — among them “Half Nelson,” “Nap-oleon Dynamite” and “Martha Marcy May Marlene” — Groth reminds simply: “Those filmmakers still managed to create great short films.”